Pressure fluctuation recorder



PRESSURE FLUCTUATION RECORDER Filed April 8, 1960 BY/Ayjwf 3&02'7426 i PRESSURE FLUCTUATHN RECRDER Charles L. English, 2204 E. 25th Place, luisa, (Dida. Filed Apr. S, 1960, Ser. Norltlt? 9 Claims. (Cl. "i3-M9) This invention relatesvgenerally to improvements in pressure measuring devices, and more particularly, to an improved apparatus tor measuring uctuations in the pressure of a liquid stream. i ,V

As it is Well known in the Aart, itis frequently desirable to measure the timesfof occurrence ci uctuat-ions in the pressure of a liquid stream, as wellwas the magnitude of eachtluctuation in such pressure; F or example, the uctuations in the press-ure of power oil being used toL oper- `ate a subsurface oil well pump provide information -hi bly y asians 'Patented Sept. 3, 1963 ICC ` tained in Ia gasv cavity against a flexible ymembrane `and rence `of the lluctu-ations in the pressure of the power oil l can be precisely determined, the eliiciency of operation of the valve mechanism, and hence the pump unit, can be ca1- oulated. Also, the magnitude of thelluctuations in the pressure. Yof the power oil 4:are highly beneficial. in the analysis Iof the pump. operation. It should also be noted that the pressure of the power oil being fed'to a subsur- 4tace hydraulic pump depends uponinany factors, but

principally upon the depth of operation of the pump. In

shallow wells the operating pressure of the power -oil at f the surface may be as low as 500 pounds and, in deeper Wells, the .operating pressure of theA power oil may be as high :as 3,860 pounds. The shifting of lthe valve mechanism of a subsurface hydraulicpump may vary the operating pressure of the powergoil as little as ten pounds.

Up to the present time, no satisfactory 4device has been available for measuring such minute iiuctu-ations.

Many different types and designs of pressure measuring devices'have been constructed. Theseprior devices vhave utilized `a pressure responsive member, such as a diaphragm, piston or tube, against which the pressure to be In most lof these prior devices,

measured is applied. v movement of the pressure responsive member is counteracted by a spring, such that movements of the pressure responsive member may be correlated withvariations in the pressure Ibeing measured. A spring or any other `mechanical type of assembly used for resisting movement of the pressure responsive'member is Iinherently limited, bothin `the range of pressures which may be measured and in sensing the magnitude of the luc'tuationsloi the f. time delay between a change in pressure and response of the device.

The present invention 'contemplates-a novel pressure responsiveV device utilizing` a piston as the pressure responsive member' exposed to the pressure being measured and which is counterbalanced by the pressure lof a coniined body of gas. The pressureof'the gas may be ad- -justed as desired when the apparatus is initially installed vide the maximum `adaptability of the apparatus.

the pressure of the gas is applied to the piston type pressure responsive member through a liquid column to proiT he membrane is of a type which will not resist variations in the volume of the body Iof gas, and the volume and pressure of the gas may be easily kadjusted by adding to or subtracting from thel liquid column extending from the membrane to the piston member.

ln its broader aspects, the present invention may be dened las `an apparatus for measuring the pressure lluetuations in a liquid llow line, comprising a housing hav ing a piston chambertherein communicating with one end of the housing, said piston chamber being reduced in diameter adjacent said Ione end Iof the housing, a piston slidingly sealed in the larger Idiameter portion 'of said piston chamber and being responsive to differential pressures `onnrthe opposite ends thereof 'for reciprocation in said piston chamber, a rodffconnected to said piston and slidingly sealed in the'reduced diameter portion of Vsaid piston chamber, mea-ns" connected to said rod for regis* tering the movements of said piston, means for imposing ow line pressure on one end ofsaid piston, a conned body of gas, and means for imposing the pressure of said body of gas against the opposite end of said piston.

` An important object of this invention is to precisely measure the occurrence of pressure iluctuations a liquid flow line, and particularly in a liquid flow line having a relatively high .average pressure.

' `[smother object of this invention is tomeasure the magnitude of `the pressure i'luctuations in ia liquid [flow line.

v A further object of this invention is to provide an apparatus for measuring the pressure iluctuations in a liquid flow line wherein movement of the pressure responsive 'member is resisted bythe pressure of a body of gas;

Another object =of this invention is to provide'an apparatus for measuring the pressure liuotuations in a liquid ilow line whichy does not require the' use of springs or other mechanical elements for counteracting the pressure of the liquid being measured.

` Another object of this invention is to provide an appar-atus for measuring the pressure fluctuations in a liquid y ow line utilizing a piston -as the pressure responsive member movable upon fluctuations in the llow line pressure, wherein minute fluctuations in the pressure of the iiow line result in substantial movements ofthe piston.

A still further object of this invention is to provide an apparatus for measuring the pressure fluctuations in a liquid flow line which is simple in construction, may be economically manutactured and which will have a long service life. f

Other objects .and advantages of theinvention will be levident yfrom the following detailed description, when' taken along cor-dance with this invention which i'nclufdes'a body l12 having `an enlarged portion 14 extendingdownwardly and outwardly from the remainder of the body '12; A cover 16 is secured `around the lower end of` the body portion ld by suitable threads i8; and adivider in thel form of a iiexible membraney Ztl is secured between the mating end laces of the. coverj 16 and body portion 14. The membr-aneltl, extends across -a substantially sphericallyy shaped cavity 22 -formed by a recess 24 in the lower end ofthe bojdyportion 14 and a recess 26 in the upper face of thercove'rrrnember 16. The membrane 20 may be formed ofA any liexible material which is substantially impervious to |gas, but which may be ilexed or bent with# out the application of any appreciable force. For example, the membrane 20 may be any `suitablerubberized or .plastic material.` The outer edge 28 of thetmembrane 20V is seal-ingly secured between the mating end faces of the lbody` portion 14 and cover 16, and the membrane 2631 is of a size to lay along either the walls of the recess 24 or the Walls ofthe recess 26. The purpose of the membrane 20 is to coniine a body of gas 30 in the lower portion of 54 to provide a reduced diameter portion 68 of `a size toL slidingly receive the rod 62. It may also benoted that the rod 62 is preferably sealed in the reduced diameter- I portion 63 of the sleeve 48l by a metal-to-metal seal.

A plurality of radial ports 70 are formed through the head portion 520i the sleeve 4S in positions to com-v municate "with the piston chamber 66y Iadjacent the re duceddiameter portion 63 of the sleeve. A circumferthe cavity 22`rand to; move vertically in the cavity 22 upon `variations in the pressure of the gas 30, as will be more fully hereinafter set iorth. c

A bore 32 extends vertically upward from the central portionY of the recess 24 into communication with a bore 34 c extending 'transversely through ythe body portion 12 above thelower enlarged portion 14. A counterbore36 is formed at the lower end of the lbore 32 to receive a porous plate 38. The .plate 38 may be formed of any j suitable 'material which will notfsubstantally restrict the ow 'of liquid therethrough and yet will prevent the membrane `from being distorted into the bore 32 during operation of the apparatus-10, as will be described. The

porous plate 38 may be secured inthe counterbore 36 in ential groove '72 is termed around the kouter periphery` of the head portion 52 between the sealing rings 54 in communication with the ports 70. -An inlet 74-is fonned in the body 12 in alignment withthewannular lgroove 72 and the ports 70 to receive l.the flow line 76 4containing the liquid being measured.y In a commercialinstallation of the apparatus 1d, the member 76 Will bea suitable connector 'communicating with theliquid tlowline, such that the pressure of the liquid in the ow line will lbei constantly communicated through Ythe annular groove 72, ports 70 .y and piston cavity 66 against thesxnaller end `64 lof the piston member Si). It may also be noted that the inlet 7.4 is threaded or otherwise suitably adapted for connection with the flow line 76.

-An equalizing passage-way 78 extends through the body 12 from the inlet '74 through a Avalve chamber 80 to the transverse bore 34 -adjacent the inner end of the-cap member 46. `A valve holder 82is secured in I'che body 12`to support a valve 84 in the chamber 80. DA valve v stem 86 extends upwardly from vthe valveA S4 and is cap member 46 whichefectively closes off the respective t end Aof thej'boref34,lffor purposes to beldescribed. v 4 c A sleeve or cylinder48 ispositioned in the transverse ,bore 34 to slidinglyvsupport a piston member Si] in the apparatus 10. The sleeve 4S' is provided with a head portion 52 of: a size to tit closely in the bore 34 in abutting `relation With'the `shoulder 42 in `the bore 34. Longitudinally `spaced sealingrings 54, such as 0rings, are secured v in mating groovesZa-round the head portion 52 to provide la `seal ofthe sleeve 48 in the bore 34, as will be described.

The main body portion S6 ofthe sleeve 48 has `an outer 34, to provide an `annular passageway from the vertical bore 32 around the sleeve 48' into the cap! member 46'. It should also be noted that a bos-s '58 is formed on the end 59 of the piston member 50l to limit movement of thepiston member -in one direction upon contact with the cap member 46. Thus, communication between the end 59 of thepiston member 50 and the upper portion of the gas lcavity 22 is established, as will be described. It may be noted here, however, that a body of liquid 60 Ais positioned inthe cap `member 48, the bore 34, the

bore 32 andin the upper portion of the gas cavity 22 above lthe membrane 20* to transfer the pressure vof the body of igas 30 iagainst'theend 59 of the piston 50'.

The .piston member 50 is slidingly sealed in the sleeve 48 for lengthwise movement in the sleeve 48 in response to dierenltial pressures on the lopposite ends there-oh In -a preferred embodiment, the piston 50 forms a metal- .tometal: seal with the inner periphery of the sleeve 48 in 'preference ,to the Iuse of piston sealing rings to minimize the force lrequired for moving the piston. A rod 62 is secured to jone end 64 of the piston S0 and extends beyond the extension 39 of the body 12 to facilitate 'f :diameter less than -thediameter of the transverse bore threadedly secured in the holder 82y threads '87 for raising andlowering the valve S4 upon turning movement of the stem 86 a manner common to the tar-t. A suitable sealing yring 38 may be secured in .theI holder 82 around the stem 86 above lthe threads yc\7:to-1:revent the t possibility of leakage upwardly through` the holder 82,

ifv desired. Also, a knob 9d is preferably secured pn the Y stem 86 above the holder 82 to facilitate the rotation of thestem 186 and loperation of the valve `84. vIt 'will be.' :apparent that when the valve S4 is raised to the position`v l shown in FIG. l', the equalizing passageway 78 will be open for the transfer of the pressure of the ow line 76 g to the bore 34, Conversely, when the valve 84 is seated on the seat 92, the passageway v7S will be Iclosed.

As shown most clearly in FIG'. 2, a bleed-'olip passageway 94 extends through the' body v12 from the bore 34 adjacent the Iheadfportion 52 of rthe sleeve |48 to the exterior of the body l2.VH Anyl suitable valve membery 96 may bese'cured inthe body 12`for cooperatingwith a valve seat 9S formed in the medial portion of the passag'eway 94 to open and close the passageway 94, as will be readily understood by those skilled in the art. 'For example, the valve 96 .maybe in the form of la screw Y simply threaded into the body 12 for vmovement toward and away from the seat 98. "It willtherefore beapparent that Ia portion of the liquid 60 may be removed through the bleed-ot passageway 94 to reduce the pressure imposed on the gas30- through the membrane 20, whichy isv particularly yuseful when adjusting the apparatus 10, vas will be described. i

Any suitable registering apparatus 100 (see FIG. l), 5 such as a recorder, may be associated with'thfe pistonV rod l62 to register the positiony andmovements'of the piston memberV 50. lIn one orm of the invention, the register 10) comprises la suitable box 102 secured tothe extension 39 of the housing `12 by suitable screws 104 in registration of the movements of the piston 50, as will be i idescribed. t It will therefore be; apparent that the bore 66 Iof-the sleeve lliforrns avtpiston cavity `for the piston member 50. 'Also, theinnendiameter of the ,sleeve k48 is preferably reduced at'a point between the sealing rings such a position that the rod 62 extends into the box 102. A chart 106 is rsupported in the box 162 by suitable drive rollers 108. Any suitable dri-ve (not shown) may be v used -for turning the rollers 103, to in turn trnove the chart Y 106 lengthwise vin the box lill.` -A scriber 110 is secured on the outer end of the rod 62 in aposition tof engage the chart I196 and provide a record lof the movements ofy the piston member Sli on the chart. i

Operation v Prior to installation vof the. `apparatus 10, the gas 30 is injected into the portion 'of the gas' cavity 22 between the membrane and recess 26 `formed in the Icover 16 at a pressure depending upon the expected average pressure of the liquid to be measured, the sizes of the opposite ends 459 and `6410i the piston member 50, kand the volume of the gas cavity 22. For example, assuming that the average pressure in the liquid flow line 76 is expected to be 2,500 pounds, and the Icross sectional sizes of [the 'opposite ends 59 and 64 of the piston member Sil lare 0x1 and 0.05 square inch, and assuming further that the volume of the gas cavity 22 is ten cubic inches, then the pressure of the lgas 30 may be in the range of 1,0114] p.s.i.a. In this example, the scriber 110 will be moved approximately one-half inch upon -a variation in the pressure of the How line 76 of approximately fifteen pounds, as will be described more in detail below.

The lgas 3l) may be injected into the :gas cavity 22m any desired manner until the desired pressure is reached. It will be V.apparent that at this time the membrane 29 will be pressed against the walls of the recess 24 and across the bore 32. However, .the porous plate 36 forms a support for Ithe membrane 20 'across the bore 32` and will prevent damage to the membrane.

When the inlet 74 is placed in communication with the llow line 76, liquid from the owline will flo-w through the .inlet 74, 4groove 72 and the ports 70 into the piston cavity 66 in contact with the smaller end 64 of the piston member Si). "Ille pressure of theliquid from the flow line 76rwill therefore move the piston member 5t) to the left, as viewed in 'FG. 1, unt-il the fboss 58 on the piston member 56 cont-acts the end of the cap member fl-6. Assuming the bleed-oil valve 96 is closed, the equalizing valve 84 is then opened to direct `:liquid 60 from the ilow line 76 through the equalizing passageway 78 into the transversebore 34 around the sleeve 4S. Tlhis liquid also flows through the cap member 46 against the larger end S9 of the piston member 50, as well as downwardly through the vertical bore 32 and porous plate 3S into the upper end portion of the gas cavity 22. It will be apparent that since this liquid, which .has been designated by reference character 6ft, has a lgreater pressure than'the gas 30, the resulting pressure Will for-ce lthe membrane 26 downwa-ndly in the gas cavity 22 `and partially compress the gas 3l) until the pressure of the gas is equalto the pressurefof the liquid. Simultaneously, the liquid 60 will react on the larger end 59 'of the pis-ton member Sil and move the piston member 5t) to the right, `as viewed in FIG. l, until the scri-ber 110 is adjacent the opposite edge of the chart 106, as indicated by ydashed lines in FIG. 1.

When the pressure of the liquid 6l) and the pressure of the gas 30 are equalized, the equalizing valve 84 is closed to prevent further communication between the inle-t 74 and the liquid 6u standing in the bore 34. vThe bleed-oli valve 96 is then opened -to bleed oil" a portion of the liquid 6i?. It will be apparent that as a portion of the liquid 6G is removed, the pressure on the larger end 59 of the piston member 50 is reduced and the scriber 110 will move from the dash line position shown in FIG. l toward fthe solid line position. Simultaneously, the gas 39 will expand in the gas cavity 22 and tend to move the membrane 2i) toward the porous plate 38 to occupy the space provided by removal of a portion of the liquid 66". ln a preferred use of the apparatus, a sufficient amount of the liquid 6l) is bled oi through the passageway '94 to move the scriber 11G to the center of the chart 106, such that the center of the chart 1% will be indicative of the average pressure in the flow lin-e 76. The bleed-olic valve 96y is closed when the scriber 110 has been moved to the desired position with respect to the chart 166.

-In most applications of the apparatus lll, as exemplified in a use for measuring the pressure fluctuations of the power oil in a subsurface hydraulic pump installation, the pressure in theilow line 76 will fluctuate both above and below the average pressure. When the pressure in the iltow line *76 increases above the average, the increased pressure is transmitted through the groove 72, ports 7l) and through the pis-ton cavity 66 against the smaller end 64 of the piston member 50. This increased force on the piston member 50 will move the piston member Si) against the pressure of the gas Si) (through the medium of the liquid 69) and cause a compression of the gas 30. When the pressure of the gas 3) applied through the liquid 6i? against the larger end 59 of the piston member 5d yis at the proper value with respect to the pressure of the ow line being applied against the smaller end 64.- of the piston member,l the piston member 5t) will become balanced and will remain in :such position. In a typical application, as indicated above, the larger tend 59 of the piston member Sil is twice the size of the smaller end 64. 'Iherefore, the forces across the piston member 5G are balanced when the pressure of the gas 30 is equal to one-half the pressure of the flow line 76.

IWhen the pressure of the llow line 76 is reduced, the force imposed on the gas 30 through the liquid 60 is likewise reduced, such that the gas 3l? tends to expand and move the piston member Si)v to the right as viewed in PIG. l (through the medium of the liquid 6b) until the forces on the piston member 50 are again balanced.

Since the pressure of the gas 30 is applied hydraulically against the piston member 50, movement of the piston member 50 will be substantially instantaneous upon a variation in the pressure in the ilow line 76; ln other words, the time `delay between movement of the scriber 116 and a fluctuation in the pressure of the allow line 76 will be reduced to a minimum, such that a graph provided by the scriber on the chart 166 will provide a true representation of the iluctuations in the pressure of the ow line 76 with respect to time. It will be understood that the chart 1tl6 is driven at a uniform speed during operation of the apparatus 10. r[he only portion of the apparatus 1t) tending to provide a time lag between a pressure fluctuation and movement of the scriber 110 is the physical movement .of the piston member 56. In a commercial application of the present invention, the piston member 'Sil will be of relatively small size, such as a tenth of a square inch in cross section, to provide alightweight member responsive to minute pressure differentials across the opposite ends thereof. It will also be apparent that since the membrane Ztl applies no force on the gas 3i), the membrane will not atleet the time response of the apparatus lll.

When the precise pressure of the gas 36 injected in the cavity 22 is known, movement of the scriber 11i) upon predetermined iluctuations in the pressure in the llow line 76 va predetermined fluctuation in the pressure in the flow line 76. As indicated above, the scriber 116` may be designed for a movement of one-half inch upon a variation of fifteen pounds in the pressure in the flow line 76, even when the average pressure in the llow line 76 is 2,50() pounds. Therefore, any desired magnitude of fluctuations may be measured, regardless of how high the average pressure in the liquid flow line 76 may be.

From the foregoing it will be apparent that the present invention provides a novel apparatus for measuring the pressure `fluctuations in a liquid llow line utilizing a piston member as the pressure responsive member, and wherein movement of the pressure responsive member is resisted solely by a body lof gas. The present apparatus requires the use of no springs or other mechanical compensating systems for resisting movement of the pressure responsive member. The apparatus will be substantially instantaneously responsive to fluctuations in the pressure in a liquid llow line, such that apparatus being operated by the liquid Isubject to pressure fluctuations may be precisely analyzed. It will also be apparent that both the occurrence and magnitude ofk pressure fluctuations may be measured, regardless of the average operating pressure of the liquid flow line connected to the apparatus. It will further be apparent that the present apparatus is simple in construction, may be economically manufactured and will have a long service life.

'Changes may be made in the combination and arrangement of parts or elements as heretofore set forth in the speciiication and shown in the drawings, it being understood that changes may be made in the precise embodiment disclosed without departing from the spirit and scope of the invention as deiined in the following claims.

I claim:

1. Apparatus for measuring the pressure fluctuations in a liquid ow line, `comprising a housing having an elongated chamber therein, a piston slidingly sealed in said chamber for reciprocation in said chamber in response to differential pressures on the opposite ends thereof, an inlet in said housing communicating with one end of said chamber and adapted for connection with the ilow line for imposing the ilow line pressure on `one end of the piston, a gas cavity having a closed end land `an open end, a movable gas-impervious divider sealed across the gas cavity, a body of gas in the cavity between the divider and the closed end of the cavity, means forming a passage from the open end of said cavity to fthe end of Isaid chamber opposite said one end, -a body of liquid extend- K ing from said dividerthrough said passage to the end of the piston associated with said opposite end of said chamber to impose the pressure of said gas against said piston in a direction opposite `to the action of the flow line pressure, and means for registering all reciprocating movements ofthe piston. y

2. Apparatus as dened infclaim 1 characterized further to include a bypass extending from said inlet to ysaid passage, and a Valve in said bypass for adjusting the pressure of said gas in accordance with the expected average ilow line pressure to be measured.

3. Apparatus as defined in claim 1 wherein the end of said piston exposed to flow line pressure is smaller than the opposite end thereof.

4. Apparatus as defined in 'claim 3 characterized further to include a bypass extending' from said inlet to said passage for imposing How line pressure on said gas, 4a valve in said bypass for stopping communication between said inlet and said passage, and a valved bleed-01T passageway communicating with said passage for reducing the pressure imposed on said gas and positioning said piston at the desired position in said chamber.

- 5. Apparatus as defined in claim 1 wherein said divider comprises a flexible membrane having the outer edges thereof sealed to the inner periphery of said cavity.

6. Apparatus for measuring the pressure uotuations in `a liquid flow line, comprising: a housing having a piston chamber 'therein communicating with one end of the housing, said piston chamber being reduced in diameter adjacent said one end of the housing, :a gas cavity carried by said housing and having an openv end and a closed end, -a piston slidingly sealed in the larger diameter portion of said'piston chamber andibcing responsive to pressure differentials on the opposite ends thereof for reciprocation in said piston chamber, a rod connected to said piston and slidingly `sealed in the reduced diameter portion of of the larger diameter portion of said piston chamber l opposite said inlet, land a body `of liquid extending from said membrane through said passage to the respective end of said piston.

7. Apparatus as defined in claim 6 characterized further to include valved passageways in said housing communicating with said inlet, said passage .and the exterior of said housing for adjusting the position of said piston preliminary to measurements of iluctuations in the flow line pressure.

S. Apparatus as defined in lclaim 7 wherein said valved passageways comprise a valved equalizing passageway communicating with said inlet and said passage for imposing the flow line pressure on said gas, and a valved bleed-oli? passageway extending fr-om said passage to the exterior of said housing for bleeding oit a portion of said body of liquid. and reducing the pressure imposed on said gas to position said piston at an intermediate position in said piston chamber preliminary to measurements of fluctuations in the iiow line pressure.

9. Apparatus as deiined inclaim 6 wherein saidgas cavity is spherical' in cross section, said membrane is secured across the central portion of said cavity :and is of a size to lay along the walls of said cavity across the open end of said cavity without stretching, and characterized further to include a porous plate secured across the open end of said cavity to retain said membrane within Isaid cavity.

References Qitedin the iile of this patent g UNITED STATES PATENTS (Addition to No. 757,515)

France Y Aug. 12, 19.35 

1. APPARATUS FOR MEASURING THE PRESSURE FLUCTUATIONS IN A LIQUID FLOW LINE, COMPRISING A HOUSING HAVING AN ELONGATED CHAMBER THEREIN, A PISTON SLIDINGLY SEALED IN SAID CHAMBER FOR RECIPROCATION IN SAID CHAMBER IN RESPONSE TO DIFFERENTIAL PRESSURES ON THE OPPOSITE ENDS THEREOF, AN INLET IN SAID HOUSING COMMUNICATING WITH ONE END OF SAID CHAMBER AND ADAPTED FOR CONNECTION WITH THE FLOW LINE FOR IMPOSING THE FLOW LINE PRESSURE ON ONE END OF THE PISTON, A GAS CAVITY HAVING A CLOSED END AND AN OPEN END, A MOVABLE GAS-IMPERVIOUS DIVIDER SEALED ACROSS THE GAS CAVITY, A BODY OF GAS IN THE CAVITY BETWEEN THE DIVIDER AND THE CLOSED END OF THE CAVITY, MEANS FORMING A PASSAGE FROM THE OPEN END OF SAID CAVITY TO THE END OF SAID CHAMBER OPPOSITE SAID ONE END, A BODY OF LIQUID EXTENDING FROM SAID DIVIDER THROUGH SAID PASSAGE TO THE END OF THE PISTON ASSOCIATED WITH SAID OPPOSITE END OF SAID CHAMBER TO IMPOSE THE PRESSURE OF SAID GAS AGAINST SAID PISTON IN A DIRECTION OPPOSITE TO THE ACTION OF THE FLOW LINE PRESSURE, AND MEANS FOR REGISTERING ALL RECIPROCATING MOVEMENTS OF THE PISTON. 